chore(deps): update dependency fsdocs-tool to v20

Author: renovate[bot]

.config/dotnet-tools.json

@@ -21,7 +21,7 @@
       ]
     },
     "fsdocs-tool": {
-      "version": "19.1.1",
+      "version": "20.0.0",
       "commands": [
         "fsdocs"
       ]